In U.S. Pat. No. 4,040,747 to Donald R. Webster issued Aug. 9, 1977, there is disclosed a relatively low cost instrument for measuring and analyzing the optical properties of organic materials to determine the percentages of certain constitutents of the test materials. This instrument was developed to satisfy a need for a low cost instrument to rapidly determine the moisture, oil and protein content in produce and grain products. In the instrument disclosed in the patent, a source of wideband infrared light is positioned to illuminate a sample through a filter assembly in which interference filters are arranged in the form of a paddlewheel mounted for rotation about the axis. As the filter wheel rotates, each filter is brought successively into the infrared light beam. As each filter is moved through the light beam by the filter wheel, the angle of incidence of the light beam on the filter changes and this changes the wavelength transmitted through the filter. Thus, in this manner, a narrow band of wavelength irradiates the sample and the narrow wavelength is scanned over a wide range of wavelengths. Each filter provides a difference range of wavelengths. By detecting the amount of reflection at selected specific wavelengths and the relationships of these reflectivities, the oil, protein and water content of the sample can be accurately and quickly determined.
The most accurate measurements are obtained from the grain sample if the grain sample is first ground and the grinding should be carried out a short time before the measurement is made. This grinding operation increases the number of steps to make a measurement and also increases the amount of time and labor to make a grain sample measurement.
The present invention provides an instrument of the type disclosed in the Webster patent, but in which the grinding is carried out automatically in the instrument at the time the measurement is made. This eliminates the separate step of grain grinding normally employed in the prior art system disclosed in the Webster patent. Briefly, in accordance with the present invention, a filter wheel assembly is provided similar to that disclosed in the Webster patent. In addition, a grinding is provided on the instrument with a hopper to hold grain to introduce into the grinder. A plate blocks the bottom of the hopper from the grinder so that it may be filled with grain prior to a measuring operation. The instrument of the present invention, like that of the Webster patent, employs a reflectivity standard which is positioned in the path of the infrared rays prior to each measurement to automatically calibrate the instrument. To initiate operation of the instrument, the reflectivity standard is pivoted out of the path of the infrared light. This action automatically energizes the grinder motor. Then, after a two-second delay to permit the grinder motor to get up to speed, grain is permitted to flow from the hopper into the grinder and the ground grain flows into a chute, the bottom of which is arranged to receive the infrared light passing through the filter wheel. The bottom of the chute is closed by an impeller to remove the grain from the chute. After a delay of five seconds sufficient for the chute to fill up, the impeller is rotated to begin to move the grain out of the bottom of the chute. At this time, the instrument begins to make measurement as the grain in the chute moves through the infrared beam in the form of a ground bed of grain. This provides an automatic averaging from the sample being analyzed.